Certain water-absorbent polymers are known to speed the growth of commercially valuable plants through improved water management. Some types of polymers used for that purpose include polyacrylate (the absorbent agent used in disposable diapers), polyvinyl alcohol, starch-based copolymers, and cross-linked polyacrylamides. Blends of such agents are also commercially available. The following U.S. Patents, for example, disclose a variety of polymers used with plants, and are incorporated by reference:
U.S. Pat. Nos. 4,985,061, 4,985,062, and 4,906,276, all issued to Hughes, disclose an aqueous gel including a highly absorbent, cross-linked, mixed salt of homopolymerized or copolymerized acrylic acid. U.S. Pat. No. 4,797,145, issued to Wallace et al., discloses a group of synthetic agricultural polymers known as polyelectrolytes used in combination with water-soluble polysaccharide. The patent discusses the application of that and a variety of different polymers to the problem of soil conditioning. U.S. Pat. No. 4,241,537, issued to Wood, discloses a dissolved water-soluble polyisocyanete capped prepolymer. U.S. Pat. No. 4,559,074, issued to Clarke, discloses a substantially non-ionic polyacrylamide cross-linked with a low amount of methylenebisacrylamide (MBE) or another agent. U.S. Pat. No. 4,320,040, issued to Fujita, et al., discloses a method of preparing hydro-gel polymers from polyvinyl alcohol and polyacrylic add. U.S. Pat. No. 3,336,129, issued to Herrett et al., is an early patent describing types of cross-linked polymers.
In general, suitable water-absorbent polymers consist of one or more granular materials that, when wetted, convert to a gel form and that are capable of absorbing and releasing water repeatedly. Suitable polymers can absorb up to several hundred times their weight in water and can repeatedly absorb and release the water for as long as a decade. When placed near the roots of plants, such polymers act as "water banks", absorbing excess water until the plant roots can tap it. When properly applied, suitable polymers can reduce the amount of water lost through percolation and evaporation, reduce the leaching of soil nutrients, pesticides, or herbicides, and improve soil aeration. Those effects improve yields and reduce watering cost significantly.
Until recently, the application of water-absorbent polymers in the agricultural field has been largely limited to improving seed germination, sprig establishment, and plant transfer. In all of those uses, the polymer is generally applied directly to the plant roots, because the plants are temporarily removed from the soil. Also, such polymers can be mixed with soil, for such applications as gardening. For example, the following references, which are also incorporated by reference, disclose such applications: U.S. Pat. No. 4,540,427, issued to Helbling (mixing with removed soil or sand); U.S. Pat. No. 4,495,724, issued to Kirkland et al. (seed coating); the above-cited Hughes patents (coating stems of freshly cut plants for transport or transplant); and the above-cited Clarke patent (mixing with potting soil or synthetic growth media such as mineral wood).
There has been a desire from some time, though, to apply water-absorbent polymers to in-ground crop and turf water-management projects, where it is impractical to remove either the plants or the soil. The potential commercial benefits from such large-scale uses far exceed the benefits achieved from out-of-ground applications. Inefficient or impractical injection means, however, have blocked or rendered impractical in situ granular polymer applications.
Attempts have been made to use standard or modified tilling machines, vibratory plows, seed drills, water-jet injectors, and coring machines to inject polymers, but such efforts have suffered from a variety of problems. Such methods typically disturb the topsoil and the plants. Such disturbance can result in growth shock to the plants. As a result, known methods are largely unsuitable for use in already planted fields, and some require polymer insertion before the plants are grown or even before they are planted.
In addition, earlier methods do not distribute the polymers evenly, thoroughly, or in the most advantageous locations. Such methods often restrict the polymers to horizontal strips on, or vertical grooves or holes in, the field. Appropriate polymers can be relatively expensive, moreover, and past methods have not applied them cost-effectively.
Accordingly, it is a primary object of the present invention to achieve practical methods and means for injecting granular water-absorbent polymers into soil to promote plant growth.
It is another object of the invention to provide methods and apparatus for injecting particle matter near the roots of plants with minimal disturbance of topsoil or plants.
It is another object of the invention to provide methods and apparatus for efficiently spreading particles below the surface into topsoil.
It is another object of the invention to provide a means of improving the yield of crops.
It is another object of the invention to provide a method of improving water management for crops and turf.
It is another object of the invention to provide methods and apparatus for applying granular water-absorbent polymers without disturbing, removing, or replanting turf.
It is another object of the invention to provide methods and apparatus for applying granular water-absorbent polymers evenly and with maximum distribution across a field and with maximum diffusion through a soil layer.
It is another object of the invention to provide methods and apparatus for controlling the locations of injected granular water-absorbent polymers to the necessary depth or range of depths for maximum effect.
It is another object of the invention to provide an improved composition of granular water-absorbent polymers suitable for improved distribution in soil and improved plant yields.
It is another object of the invention to provide methods and apparatus for injecting particles in a horizontal, subsurface plane without causing plant shock.
The present invention achieves the above and other objects by use of a device and process of injecting a blend of water-absorbent polymers, including fine granules, using one or more air-blown, plowblade applicators. The process creates a "blanket" of moisture-retaining particles for the plant roots. A further aspect of the invention includes the method of drawing the blade through the soil at an appropriate shallow angle and speed to establish a wave in the soil, together with the use of a deflector and control over the air pressure, all of which maximizes diffusion and distribution of the injected particles.
Other aspects of the invention will be appreciated by those skilled in the art after a reading of the detailed disclosure of the present invention below.